Sidewall Conveyor Belt Specifications Explained

A sidewall conveyor belt spec sheet is a contract written in numbers, and most of the numbers never get read. Buyers compare belt width, length and price, then file the rest. Six months later the cleats are coming off at a 60-degree incline and nobody can say why, even though the reason was sitting in the quotation all along.

This article decodes that document line by line: what belt strength in N/mm actually means, why cleat height and sidewall height are two different jobs, what "8/3" tells you about a cover, and which numbers reveal whether a supplier engineered the belt or just priced it. It is written from the enquiry desk at QBF Rubber, where we spend a fair part of every week explaining to someone why their current belt spec cannot do what the salesman said it would.

Every specification describes the same three structural zones, and a good spec keeps them separate because they do different jobs:

• The base belt carries the tension. Width, carcass and strength in N/mm live here.
• The corrugated sidewalls keep the material on the belt. Height is the number that matters.
• The cross cleats form the pockets that do the lifting. Profile, height and pitch all matter.

In a properly made belt these three are hot vulcanized into one unit. When a quotation prices the sidewalls and cleats as separate bolt-on extras, that is the first sign you are buying an assembly, not an engineered sidewall belt.

Nominal belt width is the full width, edge to edge. It is not the carrying width. The sidewalls sit on the outer edges, and the load cross-section sits between them, so on a 1200 mm belt with 200 mm sidewalls you are effectively carrying on less than 800 mm. A quotation that does not subtract the sidewalls when sizing capacity is overstating throughput.

Tensile strength is given in N/mm - the rated tension per millimetre of belt width. A 1600 N/mm belt at 1200 mm width is rated for 1.9 million newtons of working tension, which is why the number cannot be guessed from the material; it has to come from a tension calculation covering load, length, lift and starts. Fabric carcasses (EP, polyester warp with nylon weft) cover the range from roughly 250 up to about 2500 N/mm. Above that, or for very long centres, the spec moves to steel cord (ST construction), which is where the top end of our range - belts rated to 10,000 N/mm - lives.

A complete base belt spec names the carcass, the strength, the top and bottom cover thickness and grade, and the belt width. Anything shorter is a quote for a guess.

Sidewall height is measured from the base belt surface to the top of the corrugation, and it sets the depth of the load cross-section. Our range runs from 40 to 630 mm; on real jobs, 100 to 400 mm covers most of what gets specified. Two rules apply:

• Leave freeboard - typically 25–50 mm between the loaded material line and the top of the sidewall - or material escapes at the loading and discharge transitions.
• The sidewall must clear the cleats it works with. A clean spec states the pair, for example "sidewall 250 mm, cleats 220 mm", so nobody discovers at the splice that the geometry never closed.

Ask your supplier what corrugation profile the sidewall uses and whether it is reinforced where it meets the base belt. That junction takes the whole shear load in a steep system, and it is the first place a cheap belt fails.

Cleat profile is the shorthand that tells an experienced reader what duty the belt was designed for. The four profiles we manufacture cover the practical range:

Profile Reading the line Where it belongs T Plain cleat, economical, good general incline Standard plant conveyors up to about 40° C Self-cleaning, no bolting to the sidewall Sticky fines, light duty TC Self-cleaning with higher capacity Medium to heavy duty, the common choice TC-XS Reinforced, replaceable blade Impact loading, steep to vertical, high tonnage

Cleat height is the pocket depth and must be sized against the largest lumps in the stream - a common working rule is at least twice the maximum lump size. Cleat pitch, the centre distance between cleats, then trades capacity against clean discharge: too tight and the material cannot load properly between cleats, too wide and the pockets overload on a steep belt. A spec that lists cleat height but not pitch is a spec that has not been engineered.

Cover thickness is written as top/bottom in millimetres - "8/3" means 8 mm on the carrying side, 3 mm on the pulley side. The notation matters because the two sides work differently: the top takes abrasion and impact, the bottom takes pulley wear and is where rips telegraph from. A single thickness figure tells you the supplier thought about one side only.

Grade is tested, not claimed. Abrasion resistance is measured as volume loss under DIN 53516 / ISO 4649: standard grades sit around or under 150 mm³, premium abrasion-resistant grades under about 120 mm³, and the number is what you hold a supplier to, not adjectives like "heavy duty".

Then the compound itself: heat-resistant covers for sinter, clinker and ash; oil- and chemical-resistant compounds where the material attacks rubber; flame-retardant and antistatic construction for underground coal and tunnels, which is a standards requirement, not an option. Each of these changes the cover spec line completely, and none of them is visible in a photograph of the belt.

Three more numbers earn their keep:

• Adhesion between cleat, sidewall and base belt. We bond at more than 17 N/mm. If the quotation does not state a bond strength, the cleats are probably glued on, and glue is what fails first on steep duty.
• Splice type. Hot vulcanized step splices for fabric belts, single-step splices for steel cord. A spliced joint is the strongest link or the weakest one depending entirely on who cures it.
• Minimum pulley diameter. Corrugated sidewalls are compressed at every pulley wrap. A spec that ignores pulley geometry will deliver a belt whose sidewalls fatigue and crack from the inside, no matter how good the rubber is.

The same number means different things under different test methods, so every spec should name the standard it is tested against: DIN 22102 and EN/ISO 14890 cover fabric conveyor belts, ISO 15236 covers steel cord, and regional buyers often work to AS, JIS, SANS or RMA grades. Fire performance for underground use is regulated separately, under EN 14973 and related requirements. When a quotation gives values without a standard, assume the most convenient test was used.

Below is what finished specifications look like for three very different duties. The numbers are illustrative - a real spec must come from calculation - but the structure is exactly what a supplier should be able to return to you within a day of receiving your enquiry.

Spec line Mining: iron ore, vertical lift Cement: clinker, steep incline Port: coal, high tonnage Throughput 900 t/h 450 t/h 2000 t/h Geometry Vertical, 60 m lift 65° incline, 25 m lift 45° incline, 15 m lift Belt width 1600 mm 1200 mm 1400 mm Strength / carcass ST1250 steel cord EP1250 fabric EP1600 fabric Sidewall height 400 mm 250 mm 200 mm Cleat TC-XS, 360 mm high TC, 220 mm high TC, 170 mm high Cleat pitch 500 mm 450 mm 400 mm Cover 8/3, abrasion-resistant 8/3, heat-resistant 6/2, standard grade Adhesion >17 N/mm, hot vulcanized >17 N/mm, hot vulcanized >17 N/mm, hot vulcanized Standards ISO 15236 / customer spec EN 14890 / DIN 22102 AS 1332 or RMA

Notice the pattern. Mining spends its spec on strength and impact - steel cord, TC-XS, heavy covers - because tension and lump impact kill those belts. Cement spends it on the heat-resistant compound and self-cleaning cleat profile. Port spends it on width, throughput and splice quality, because downtime at a berth costs more than any belt. The material and geometry drive the spec; the spec is just the paper trail of that thinking.

1.No adhesion value. If the cleat-to-base bond strength is absent, assume cold bonding and price in the early replacement.

2.Cover thickness as one number. "6 mm cover" instead of "6/2" means the carrying side is thinner than it looks.

3.Cleat pitch missing. Height without pitch is like a gear with teeth but no spacing spec.

4.Strength quoted only in plies. "5-ply EP" without N/mm cannot be checked against your tension calculation.

5.Sidewall height that ignores your lump size. A tall sidewall with undersized cleats still rolls material backwards on a steep belt.

6.No standard named. Values tested to a convenient method are values you cannot enforce.